A simple method for the quantification of a class of labile marine pico- and nano-sized detritus: DAPI Yellow Particles (DYP)

A simple and rapid method for microscopic quantification of an abundant class of labile pico-and nano-sized detrital particles (0.2 to 20 pm), using the fluorochrome stain DAPI, is described. Using an appropriate UV-filter set, examination of DAPI-stained samples revealed not only blue (DNAcontaining) but also yellow particulate matter. We showed that DAPI yellow fluorescing particles resembled detritus made from plankton tow material or copepod faecal pellets and were almost exclusively organic, enzyme-degradable matter. Quantification of the total surface area of these particles in the Ligurian Sea (NW Mediterranean) revealed stocks averaging 80 mm2 I-' in surface layer waters.